WE2408 查看數據表（PDF） - Unspecified

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WE2408

2.4GHz Single Chip FM Transceiver

Unspecified 

WiNEDGE & WiRELESS

Winceiver WE2408

2.4GHz Single Chip FM Transceiver

LPF2 (I/Q)

This second stage of the I/Q baseband low pass filter (LPF) section consists of active,

transconductance (gm) type filters. Combined with LPF1, these filters provide the required channel

selectivity by passing the entire desired frequency spectrum, while attenuating noise and adjacent

channel interference outside of the desired signal’s bandwidth.

DC Offset Correction

A proprietary DC offset correction circuit is used to control DC offset voltages. The use of DC offset

correction improves dynamic range, minimizes LO feed-through in the up-conversion mixer, and

reduces signal distortion. The correction circuit operates automatically and in a continuous mode.

Up-Conversion Quadrature Mixer

The zero-IF, complex, filtered baseband signal is translated by the quadrature up-conversion mixer to

an intermediate frequency (IF). The resultant up-converted IF signal is low enough in frequency to

provide adequate SNR at the output of the period-to-digital FM demodulator, yet high enough to

satisfy signal sampling criterion.

IF BPF

The band pass filter, after the quadrature up-conversion mixer, passes the IF signal and rejects the

harmonic components of the up-conversion mixer's local oscillator. The IF band pass filter is

comprised of cascaded, active, transconductance filters with Butterworth response characteristics.

The lower corner frequency of the IF BPF is fix at 8kHz. The higher corner frequency of the filter is

determined by an external resistor connected to IFSET pin.

RSSI

The receive signal strength indication (RSSI) circuitry incorporates a log amplifier and detector for the

purpose of measuring the received RF carrier power level.

Period-to-Digital FM Demodulator

The Period-to-Digital (P/D) FM demodulator digitize the half-cycle period of the IF signal and convert

that information into the demodulated FM audio signal via a digital to analog converter.

The digitizing clock signal for the P/D is derived from the Rx VCO oscillator and the P/D divide ratio

(PDR). The PDR is programmable via serial interface.

TRANSMITTER

The transmitter section of the WE2408 is comprised of a modulation input circuit, a PLL synthesizer /

VCO, and a RF power amplifier (PA) capable of providing -4.0 dBm into a 50: load. A description of

each major function block follows:

Transmit PLL Synthesizer and VCO

The transmit (Tx) on-chip PLL synthesizer is identical to the receive PLL synthesizer except that it

contains only a 3 x multiplier after its VCO. The transmit VCO frequency is therefore 1/3 the

transmitter local oscillator.

The transmit PLL accepts modulation audio to provide a frequency modulated (FM) RF carrier.

Utilizing a direct modulation approach, the modulation voltage is directly applied to the PLL loop filter.

© 2003 WiNEDGE & WiRELESS PTE LTD

Rev Date: 2003 May 23

Page 8

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